Voltage regulator circuit



July 6, 1948- A. H. SCHOOLEY VOLTAGE REGULATOR CIRCUIT Filed June 19,1943 nsauafzo ourPur LE'ii-E gvwwwbo'b ALLEN H. SCHOOLEY Patented July6, 1948 UNITED STATES PATENT OFFICE VOLTAGE REGULATOR CIRCUIT Allen B.Schooley, Washington, D. 0.

Application June 19, 1943, Serial No. 491,470 1 Claim. (01. 323-89)(Granted under the act oi March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) This invention relates to avoltage regulator and more particularly to a means for stabilizing theoutput from a line controlled transformer.

In many of the current radio circuits voltage regulation is of primeimportance since minute voltage changes may effect the operatingcharacteristic of the entire circuit. Most voltage regulators providedby the prior art relate to B supply and bias regulation. Filamentvoltage regulation, however, is also of primary importance since changesin filament voltage will also effect the operating characteristic of thevacuum tubes in the circuits.

It is therefore, an object of this invention to provide a voltageregulator for use in controlling the output of a transformer.

It is another object of this invention to provide a filament voltageregulator.

It is another object of this invention to provide a voltage regulatorwhich is equally responsive at all frequency changes.

Other objects and features of the present invention will become apparentupon a careful consideration of the following detailed description whentaken together with the accompanying drawings, the figures of which aredesigned for the sole purpose of illustration and not as a definition ofthe limits of the invention, reference being had for the latter to theappended claim,

Fig. 1 is a schematic diagram of a preferred embodiment of the presentinvention, and

Fig. 2 is a schematic diagram of one modification of the presentinvention.

It is contemplated by the present invention to provide a means forregulating the output of a transformer by utilizing the change in outputvoltage to control the exciting current of the transformer, and moreparticularly to control the impedance in the primary circuit of thetransformer. The manner in which I propose to accomplish the foregoingis through the utilization of the output voltage from the transformer asa control means for regulating the thermionic emission of a vacuum tubeand consequently the conductivity of the tube, which in turn operates tocontrol a serially connected impedance in the primary circuit of thetransformer.

Reference is had more particularly to Fig. 1 wherein there is shown apreferred embodiment of the present invention, comprising a transformerID the output voltage of which it is desired to regulate, having a pairof input terminals II and II and a pair of output terminals l2 and I2.Across this latter pair of terminals there is connected a filamentaryheater it of the diode H, which in turn contains a, serially connectedresistance I! for use in regulating the heater current. The primarywinding of a second transformer I3 is connected in shunt with the heaterI, while one side of the secondary winding thereof is connected to oneof the output terminals l2 and the other side through resistance I! tothe plate of diode I4. The latter connection provides the plate of diodeH with a pulsating positive voltage. As shown in the Fig. 1 the outputof diode I4 is fed to the control electrode 2| of the first tube I9 of apair of serially comiected direct coupled amplifiers l9 and 20. Sincethese amplifiers are direct coupled they are equally responsive at allfrequencies. The output of this direct coupled amplifier circuit is fedin parallel to the respective control electrodes 25 and 26 of the tubes2i and 22. The plates of these last two mentioned tubes are connected inpush-pull by way of the secondary winding of transformer 23, the primarywinding of which is serially connected to the primary winding oftransformer ll. A source of plate potential for the direct coupledamplifier circuit comprising tubes l9 and 20 is supplied at 28.

Normal operation of the circuit is as follows: Resistance I1 isregulated to run heater IS a little colder than usual 1. e. apredetermined amount below rated heater voltage so as to draw 9.normally fixed plate current and produce the desired voltage drop acrossresistance 18. This voltage drop provides a source of input to tube l9and consequently produces the desired bias for the control electrodes 25and 26 of tubes 2| and 22 by virtue of the amplification of the directcoupled amplifier circuit. The bias on the last mentioned tubes controlsthe current passage through these tubes and consequently the load on thesecondary winding of transformer 23. The load on the secondary of thistransformer is reflected to the primary winding thereof to sustain thedesired exciting current in transdrop across the primary winding of thelatter in response to the impedance reflected by trans-' former 23 whichin turn is under control of the thermionic emission of the diode heaterI6.

I have found that the thermionic emission of diode I4 is very responsiveto slight changes in heater voltages especially when the diode heater isoperated slightly colder than normal as in the present instance. Thuslet it be assumed that for some reason an increase in output voltage isoccasioned. which increases the thermionic emission of heater l3 andthereby increases the voltage drop across resistance II. This increasein voltage drop appears as a negative bias to the control electrode 24of tube It which causes the plate voltage of this tube to rise andconsequently the plate voltage of tube III to drop. The drop in platevoltage of tube 20 appears as a negative bias to the control electrodes25 and 28 of tubes II and 22 to decrease the current flow throughthesetubes which in eflectproduces a decrease in load on the secondaryof transformer 23. The decrease in load of the secondary isrefiected'into the primary winding of this transformer as a highimpedance to reduce the exciting current or transformer iii andconsequently decrease the output voltage thereof. Thus if a decrease inoutput voltage was occasioned the reverse action of the amplifiercircuit and tubes 2i and 22 would result to cause an increase inexciting current to transformer Ill and consequently an increase inoutput voltage therefrom.

The operation of the circuit shown in Fig. 2 is identical to thatcircuit shown in Fig. 1, with the exception that this circuit involvesthe use of an additional transformer 21, and the resistance II is madevariable in order to regulate the input to the amplifier circuit andhence the magnitude of the bias voltage supplied to tubes 2| and 12.Therefore, further explanation of this circuit is believed to beunnecessary.

Although I have shown and described only certain and specificembodiments of the present invention, I am fully aware of the manymodifications possible thereof. Therefore this invention is only to berestricted except insofar as is necessitated by the prior art and thespirit of the appended claim.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmentalpurposeswithout the payment of any royalties thereon or therefor.

I claim:

A means for regulating the output voltage of a transformer, comprising athermionic vacuum tube having a filamentary heater and a plate, saidheater connected across the output terminals of said transformer in sucha manner that its thermal emission varies in accordance with the changein output from said transformer, a resistance means disposed in serieswith said heater and adjusted to operate said heater at a predeterminedvalue below its rated voltage, an amplfier circuit, means connecting theoutput of said vacuum tube to the input of said amplifier circuit, apair of electron discharge devices each having an anode, a cathode and acontrol electrode, a sec- REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,935,413 Prince Nov. 14, 1933Philpott Jan. 5, 1937

